x-(20x分之3）=37.4
两边同乘以x
==>x^2-0.15=37.4x
==>x^2-37.4x-0.15=0
==>(x-18.7)^2-18.7^2-0.15=0
==>(x-18.7)^2=18.7^2+0.15
==>(x-18.7)^2=349.805
作近似运算
==>x-18.7=18.703或-18.703
==>x=0.003 或-37.403
作近似运算
==>x-18.7=√349.805或-√349.805
==>x=-18.7+√349.805或-18.7-√349.805